Many distinguishing characteristics began to emerge with the evolution of Australopithecus. Most notably was the appearance of pronounced bipedalism combined with an advance in brain capacity to approximately 500 cm3. Primarily vegetarian, Australopithecus were social and used such groups to forage for food.

Anatomical features in Australopithecus were distinct from earlier Hominids. The teeth and jaws evolved to function together for grinding and processing food. The robust Australopithecine advanced further in this respect, developing huge, flat molars and small knife-like canines and incisors. In all forms of Australopithecus, the teeth became tucked into the face more than its ancestors, making the facial profile more flat and aiding in chewing food.

The most important differences between Australopithecus and earlier Hominids is the evolution of jaw and skull structures and the emergence of bipedalism. The post cranial skeletons of all variations of Australopithecus are similar, excepting the features of height and weight.

1 Some sources claim that A. afarensis is a robust Australopithecine. Skull and jaw formation in this species could arguably be either; a photograph found at http://dekalb.dc.peachnet.edu/~pgore/students/s97/bonetgar/afaren.jpg suggests to me a more slender jaw structure.